1. Field of the Invention
This invention relates to a process for the production of zeolite granules of high apparent density which have a pronounced adsorption capacity for liquid active substances and to the use of the zeolite granules as an intermediate product in the production of detergents.
2. Discussion of Related Art
German patent application 33 16 513 (Benckiser) relates to granules which are produced by spray-drying of aqueous slurries and which contain finely powdered zeolites and salts of (co)polymeric carboxylic acids. They have an apparent density of only 560 to 610 g/l. Granules containing zeolites, salts of (co)polymeric carboxylic acids and, in addition, small quantities of alkali metal silicates, which are used as a support material for liquid detergent constituents, more particularly nonionic surfactants, are described in German patent application 34 44 960. The apparent density of these granules, which are produced by spray drying, is at most 700 g/l and is preferably between 500 and 650 g/l.
Granules containing zeolites and alkali metal silicates which have a particle size of 0.15 to 2 mm and an apparent density of 300 to 700 g/l are known from European patent application 21 267 (PQ). They are also suitable for the adsorption of liquid detergent constituents, particularly nonionic surfactants. For the production of these granules, a dry premix of zeolite and alkali metal silicate (mixing ratio 1:1 to 1:8) is sprayed with water and agglomerated in a granulator, after which the excess water is removed by drying to a residual content of less than 5% by weight. The disadvantage of these granules is, above all, the high content of alkali metal silicates showing a strongly alkaline reaction which severely restricts the use of these granules in detergents showing a neutral to mildly alkaline reaction of the type suitable for delicate fabrics. In addition, apparent densities of more than 700 g/l cannot be obtained in accordance with the teaching of this document. According to European patent application 149 264 (Unilever), commercially available spray-dried zeolites or mixtures thereof with inorganic salts, such as sodium sulfate, can be used for the adsorption of liquid detergent constituents, particularly nonionic surfactants. The apparent density of the relatively finely divided spray-dried products is in the range from 450 to 600 g/l, the particles ranging from 0.05 to 0.5 mm in size.
German patent application 38 38 086 describes the production of granules from zeolite and the sodium or potassium salts of polymeric or copolymeric carboxylic acids, the agglomeration or granulation process taking place with addition of a granulation liquid and the agglomerate obtained being dried to obtain free-flowing granules having an apparent density of 750 to 1,000 g/l. To produce the granules, a homogeneous powder-form mixture of zeolite and the salt of the (co)polymeric carboxylic acids is prepared and granulated in another mixing and granulation stage with addition of water which is preferably sprayed onto the agitated powder mixture. The polycarboxylates are initially introduced in solid form and are not added in dissolved form as part of the granulation liquid because the quantity of granulation liquid used is a critical factor and, accordingly, has to be exactly measurable. Excessive quantities of granulation liquid lead to granules having a broad particle size distribution and an undesirably large coarse component (particle size above 2 mm in length (and also to a relatively low apparent density.